Industrial and manufacturing facilities typically employ large electrically powered machines to provide the horsepower and motive forces needed for production. Proper operation of such machines is often essential to meeting production needs. To this end, production facilities often adopt predictive maintenance programs in which machines are periodically monitored to ensure proper operation. Many predictive maintenance programs employ vibration analysis as a way to assess the health of the machine. During vibration analysis, a vibration sensor, or accelerometer, is positioned against the machine to be monitored and the accelerometer output is analyzed to detect the presence of anomalous operating conditions.
A variety of methods are used for maintaining contact between the accelerometer and the machine being monitored. For example, the accelerometer can be configured to be manually held against the machine as data is taken. Other methods allow for permanent attachment of the accelerometer to the machine (such as by threaded fastener or adhesive) to enable hands-free taking of data. However, such permanent mounting methods are less than desirable due to the labor and costs involved, and the use of attachment methods which do not permanently affix the accelerometer to the machine have historically proven to be disadvantageous as a result of poor sensor response.
During the data collection process, it is often desirable to collect machine vibration data in multiple directions or axes (e.g., radial, vertical and axial). Stress wave measurements should also be acquired in at least one of the directions. Traditional data collection techniques call for mounting a single-axis sensor to sense vibration along one axis, waiting for the sensor to settle, acquiring data, and then repeating these steps for all other axes for which data is needed. When collecting data along multiple axes, the process is time consuming, inefficient, and susceptible to error as the sensor must be precisely aligned along each axis to ensure accuracy and repeatability.
Multi-axis vibration sensors have been available for a few years, but they have not been generally accepted as an alternative to single axis sensors for portable condition monitoring. One reason for this is the difficulty in properly mounting a traditional multi-axis sensor to the machine. Each time the sensor is mounted it must be properly oriented in a plane tangent to the surface of the machine and it must be torqued down on a very clean, smooth surface to maintain adequate bandwidth. The efforts required to mount these sensors is generally seen as outweighing any savings gained by not having to multi-mount a single axis sensor.
What is needed, therefore, is the ability to efficiently obtain accurate vibration data along multiple machine axes employing a multi-axis vibration sensor.